Method of cooling hot dipped galvanized,continuously moving workpieces

ABSTRACT

A PROCESS OF COOLING A HOT DIPPED GALVANIZED, CONTINUOUSLY MOVING WORKPICE BY PASSING THE GALVANIZED WORKPIECE OVER AN IDLER ROLL HAVING A FERRIC OXIDE COATING ON ITS OUTER SURFACE AND DIRECTING A COOLING FLUID AT THE POINT OF CONTACT BETWEEN THE ROLL AND THE SURFACE OF THE GALVANIZED WORKPIECE. THE OXIDE COATING ON THE ROLL HAS LITTLE OR NO AFFINITY FOR THE GALVANIZED COATING.

Oct. 17, 1972 J. T. MAYHEW 3,698,938 METHOD OF COOLING HOT DIPPED GALVANIZED, CONTINUOUSLY MOVING WORKPIECES Original Filed March 19, 1970 /N VEN TOR JOHN T. MAYHEW p D D D D DU 1 HIS ATTORNE Y5 United Smtes Patent 015cc 3,698,938 Patented Oct. 17, 1972 US. Cl. 117-114 A 4 Claims ABSTRACT OF THE DISCLOSURE A process of cooling a hot dipped galvanized, continuously moving workpiece by passing the galvanized workpiece over an idler roll having a ferric oxide coating on its outer surface and directing a cooling fluid at the point of contact between the roll and surface of the galvanized workpiece. The oxide coating on the roll has little or no afiinity for the galvanized coating.

CROSS REFERENCE TO RELATED APPLICATION This application is a division of my co-pending application No. 20,945, filed Mar. 19, 1970, now Pat. No. 3,611,530, entitled Anti-Pickup Roll Construction and Utilization for Plating Lines."

The invention relates to the method of making and utilizing an improved guide roll construction and utilization for workpieces that are being moved from a plating bath such as a hot dip galvanizing bath or dip. An important phase of the invention deals with eliminating the adverse effects of roll pickup of portions of coating material from a coated or plated workpiece.

The overhead or cooling tower guide roll for a galvanizing or zinc coating line has heretofore tended to pickup the zinc containing coating or galvanizing metal from a previously applied or dipped and still hot workpiece as it is advanced thereover. This pickup not only causes a loss of coating from the standpoint of the workpiece, but progressively builds-up on the roll surface and particularly gives rise to great difficulty in a so-called continuous line operation. The picked-up and retained coating will tend to mar the finished surface of a workpiece during its movement thereover and irrespective of whether or not the roll is of an idler or of a driven type. The processing line must be frequently stopped to remove such surface adhering coating material.

There have been many attempts to eliminate the above difficulty, such as the use of a glass cover, the use of a stainless steel roll, or the employment of a continuous buffing action on the surface of the guide roll. It has been found that bufiing actually makes subsequent pickup much more easy and, as a result, the present-day practice has been to use either the glass cover or a stainless steel roll and to try to knock-off the picked-up material rather than scrape it from the roll.

In view of the above, it has been an object of the invention to provide a solution to the problem heretofore presented from the standpoint of roller-guided movement of a workpiece after it has been plated or hot dip galvanized.

Another object has been to provide an inexpensive, practical and efiicient roll construction for substantially eliminating the pickup of galvanized coating material from a hot dipped workpiece.

A further object of the invention has been to devise a composite or two-part roll construction which will provide for and enable the utilization of a ferric oxide peripheral surface on the roll which surface has little or no afiinity for the galvanized coating.

A still further object of the inventioin has been to provide improved procedure for roll-guiding of a hot galvanized workpiece through a cooling tower or the like.

These and other objects of the invention will appear to those skilled in the art from the illustrated embodiment and the claims.

By way of illustration, FIG. 1 is a somewhat diagrammatic fragmental view in side elevation illustrating the utilization of a typical hot galvanizing or plating line with a cooling tower and its tower roll.

FIG. 2 is a horizontal side view of a roll constructed in accordance with the invention.

FIG. 3 is an end section of the roll of, on the scale of and taken along the line 3--3 of FIG. 2; it further illustrates means for utilizing the roll in an optimum manher with an inert gas, also in accordance with the invention.

And, FIG. 4 is a somewhat diagrammatic view of slightly larger scale than and taken along the line 4-4 of FIG. 1.

A guide roll such as used in an overhead relation in the cooling tower of a galvanizing line is usually operated as an idler roll. I have conceived of utilizing an especially constructed sleeve which will not require brushing or conventional hammering operations for removing adherent coating material. It also eliminates the need for expensive material, such as stainless steel.

In accordance with the invention, a metal sleeve 15 of, for example, an inexpensive, relatively low carbon steel (less than about .90% C.), is formed to substantially the full, strip-receiving effective length or width of a guide roll C of a suitable shape-retaining thickness, such as of at least about 24 gauge, but preferably of heavier thickness. The sleeve 15 is shown provided with notch, recess, concave or groove portions 15a, each having an intermediate or maximum depth of about M; of an inch, and as being equally spaced along the sleeve. For example, the valley or groove portions 15a of open annular shape may have about 3% inch centers with 1% inch banding widths to give a spacing therebetween of about 3 inches. Each groove portion 15a may be formed as a segment of a 1% inch circle and defines an annular fluidflow passageway about the sleeve 15 and with respect to the opposed surface of a workpiece that is to be substantially continuously moved thereover.

The sleeve 15, after having been shaped and provided with groove portions 15a, is given a passivizing heat treatment and its surface oxidized. This may be accomplished by annealing it at a temperature of about 1800 F., soaking for about four hours, cooling and then machining and polishing. The sleeve 15 is given a high mirror finish by the machining and polishing. It is then subjected to or given a second or normalizing treatment at a lower temperature of about 1200 F., soaked for about two hours, and thus provided with a so-called blue anneal. In the next step, the blue annealed sleeve is pickled in a hydrochloric (muriatic) acid until all scale is removed. The pickling is followed by a first rinse in cold water, a second rinse in hot water and a final rinse in cold water. After having been removed from the cold water, it is permitted to dry at room temperature and to rust until an adherent relatively finely textured, ferric (red) oxide at least covers its outer peripheral surface.

It has been determined that the thus conditioned steel sleeve 15 is very passive after annealing and rusting, and that its surface has no afiinity for the galvanized coating, whether or not it is of substantially pure zinc or contains aluminum as an alloy, for example, about .30 to .80% of aluminum, with the remainder being zinc. The special grooving on the sleeve 15 is important in facilitating or speeding the removal of heat to thus keep the roll cooler and prevent warping of the roll C as well as of the workpiece B.

The construction also makes practical an optimum operation wherein an inert gas or fluid, such as nitrogen, is sprayed or applied between the peripheral surface of composite roll C and the under surface of entering workpiece B. It provides a thin film between the workpiece and the surface of the roll, as furthered by the use of the spaces or passageways provided by the portions 15a. The nitrogen functions to not only cool the workpiece and the roll, but also aids in keeping the applied gulvanized coating non-reactive to the roll surface. In this connection, the cooling rate may be controlled by regulating the temperature of the fluid and its rate of application. The application of such a gas is particularly advantageous when a relatively heavy gauge of workpiece is being processed which, by reason of its body, will tend to be more retentive of the heat having, for example, a temperature of about 600 F. at the point of entry to the roll C. It is also particularly advantageous where, as here, a continuous high speed movement of a strip workpiece B is contemplated. It provides a non-reactive cooling agent which serves also as a protecting means for the strip B to supplement the cooling action of air blasts that may be applied to the strip in its movement from a galvanizing bath or pool E up through a cooling tower A.

In FIG. 1, A represents a typical cooling tower into which and upwardly along which a workpiece, such as a continuous strip B, is moved for cooling purposes after it has passed through a hot dip pit or the tank E in a galvanizing line. Also, in this figure, C represents an idler tower roll over which the hot galvanized strip or sheet may be continuously passed for accomplishing a guided cooling action. The roll C, as shown in FIGS. 2 and 3, has a primary, inner, base or main body part of solid cylindrical shape and the sleeve or collar part may be mounted thereon in a conventional manner, as by a frictional or sweat-on fit to, in effect, become an integral covering part thereof. As previously indicated, the sleeve part 15 has a series of annular valley or groove portions 15a in a spaced-apart relation therealong that are preferably equally-spaced longitudinally of the roll; each grooved portion 15a represents a segment of a circle, has a concave shape, with its greatest depth at the mid point of its width. The groove portions 15a provide cooling spaces along the roll C and, in effect, passageways for the reception and flow movement of the inert gas, such as nitrogen, when applied along the width of the metal strip or workpiece at substantially the point of entry or initial engagement of the galvanized strip B with assembled, composite roll C. See the spray header J of FIGS. 1, 3 and 4 which will preferably have a width substantially corresponding to the width or the sleeve 15 to apply the fluid or gas along its full transverse extent.

The sleeve 15 is especially constructed for its utilization as a strip engaging surface that is resistant to the hot-applied coating on surfaces of the workpiece B. The sleeve 15 may be either first formed with the groove portions 15a or, as an alternative, the main body 10 may have groove portions formed thereabout and the sleeve, if of relatively thin section, may be slid endwise thereon and then shaped or rolled to conform thereto and to provide complementary groove portions 15a. The sleeve 15 is fully conditioned, as in accordance with the previously described procedure, to have a red oxide or rusted surface thereon before it is applied to the main body 10 and utilized in guiding the workpiece B thereover.

In FIGS. 3 and 4, the spray jet header J for applying an inert fluid or gas, such as nitrogen, between the surface of the galvanized workpiece or strip B and the peripheral surface of the roll C has, as illustrated, a location immediately adjacent to and in front of the roll C for introducing the gas at the point of entry or engagement of the under surface of the galvanized workpiece B with the roll C. The gas is shown being supplied under positive pressure from a suitable source, such as a pressure tank F, along line G, through a control valve H and, if desired, through a cooling unit I along line D and out through spray header 1, The pressure of application may vary, depending upon the speed of the workpiece but, in general, may be in the neighborhood of about 33 to 50 pounds per square inch. For maintenance purposes, the sleeve 15 may be replaced on the main body 10, since the main body, itself is subject to minimum wear and tear, and further, since it can effectively be maintained at a much lower operating temperature employing the invention.

It will be apparent to those skilled in the art that various modifications may be made in the disclosed representative apparatus and procedure without departing from the spirit, scope and content of the invention.

I claim:

1. In a method of guiding a substantially continuously moving workpiece along a cooling tower after it has been hot dip galvanized in a plating line, passing the hot dipped workpiece over an idler roll having an adherent ferric oxide coating about its outer peripheral surface, and applying and maintaining a cooling fluid between opposed engaging surfaces of the workpiece and the roll while advancing the workpiece over the roll.

2. In a method as defined in claim 1, also supplying the cooling fluid along spaced-apart annular fluid flow passageways between the opposed surfaces of the workpiece and the roll.

3. In a method as defined in claim 1, the cooling fluid being an inert gas supplied under positive pressure at a point of entry of the under surface of the workpiece to the roll.

4. In a method as defined in claim 3, the inert gas being also supplied under positive pressure along widthwise spaced-apart annular fluid flow passageways between immediately opposed surfaces of the workpiece and the roll.

References Cited UNITED STATES PATENTS 1,965,340 7/1934 Heinicke 148-635 X 2,010,941 8/1935 Bradley 117-114 A X 2,062,795 12/1936 Pike 117-119'.2 X 2,952,568 9/1960 Diehl et al. 117-114 A X 3,148,080 9/1964 Mayhew 117-114 A X 3,323,940 6/1967 Sievert 117-114 A 3,343,930 9/1967 Borzillo et al.

3,383,189 5/1968 Sendzimir 117-114 A X 3,511,686 5/1970 Withrow 117-114 A X 3,553,004 1/1971 Schnedler 117-114 A 3,608,520 9/1971 Caldwell et al.

RALPH S. KENDALL, Primary Examiner J. R. BATTEN, JR., Assistant Examiner US. Cl. X.R. 

